A haptic indicator for motor vehicles is described in European Patent No. EP 0 348 691 A2, which in combination with a proximity-warning device gives the driver an appropriate signal when a minimum distance with respect to the preceding vehicle is undershot. Vibrations of the vehicle or its parts such as the steering wheel or the driver's seat are provided as a haptic signal. The vibrations are caused for example by an intermittent interruption of the ignition of the engine.
German Patent Application No. DE 198 57 992 shows a device for kinesthetically signaling the driver of a motor vehicle if in a system for controlling the travel velocity a shutdown is imminent or has occurred, caused by a malfunction or intentionally, or if in a system for controlling the travel velocity a set maximum value of the deceleration is not sufficient to avoid a collision of the controlled vehicle with a preceding vehicle or an obstacle, means being available, which modulate a brake setpoint value or a variable derived from it in such a way that the motor vehicle under goes a deceleration fluctuating over time that is noticeable by the driver.